1. Field of the Invention
The present invention relates to a light guide panel and a display device. More particularly, the present invention relates to a color light guide panel and a liquid crystal display (LCD) having a color light output structure.
2. Description of Related Art
With development of the photoelectric technology and the semiconductor technology, flat panel displays (FPD) such as LCDs gradually become popular in the market. Generally, the LCD includes a backlight module and an LCD panel, wherein the LCD panel is composed of a thin-film transistor array substrate, a color filter substrate and a liquid crystal layer disposed there between.
In case that the conventional color filter substrate is applied, each single pixel is composed of three sub-pixels, and a thin-film transistor is utilized for each of the sub-pixels to control intensity of light passing through the sub-pixel. The light passing through the sub-pixels is modulated by color filter patterns (red, green and blue) corresponding to the sub-pixels, so as to mix the original colors of the sub-pixels to be a color of the pixel. Accordingly, after the light passes through the color filter substrate, a luminance thereof is decreased. Moreover, material cost of the color filter substrate occupies about 15% of that of the LCD panel, and a relatively long time is required to fabricate the color filter substrate. Therefore, based on the conventional technique, an LCD without the color filter substrate is developed.
U.S. Pat. No. 6,480,247 provides a color display device without applying of the color filter substrate. According to FIG. 1 of the U.S. Pat. No. 6,480,247, a field sequential color (FSC) technique is disclosed, by which three primary color (red, green and blue) light sources are timingly switched, and transmissivity of the liquid crystal pixel is synchronously controlled during displaying of each color light source, so as to adjust a relative light amount of each primary color. Next, based on a visual staying principle, the color is perceived by human eyes. Namely, the conventional method of mixing colors on a spatial axis now can be substituted by mixing colors on a time axis, i.e. swiftly switching the R, G and B primary colors. If a switching time thereof is less than a time that can be perceived by human eyes, a mixing color effect is then achieved based on the visual staying principle of human eyes. However, in such technique, a response speed of the liquid crystal and color separation control are essential. Generally, if the response speed of the liquid crystal is not quick enough, it can be an obstacle for the color sequential technique. Moreover, to improve the color separation, a complicated control algorithm and a powerful circuit driving capability are required, so that it is hard to be implemented.
On the other hand, U.S. Pat. No. 7,164,454 provides a technique of applying a RGB LED backlight module to avoid utilization of the color filter substrate. According to FIG. 2 of the U.S. Pat. No. 7,164,454, by fabricating transparent gratings on a light guide panel, an incident light can be diffracted by the gratings. Since first-order diffraction angles formed by different wavelengths are different, light with different wavelengths can be focused at different positions on a diffusion plate via a micro-lens array, so as to achieve the RGB color separation effect. However, since requirement for alignment accuracy of the transparent gratings and the pixels is relatively high, it is hard to be fabricated.